1. Field of the Invention
The present invention relates to a method of fabricating a liquid crystal display, and more particularly to a method of fabricating a liquid crystal display wherein a liquid crystal is placed in position before an upper plate is bonded to a lower plate.
2. Discussion of the Related Art
Generally, a liquid crystal display (LCD) includes an active matrix driving system of thin film transistors (TFT""s) that act as switching devices. Since such LCDs can be made small and lightweight, they have become widely used as monitors for personal computers and notebook computers, in office equipment such as copy machines, and in portable equipment such as cellular phones and pagers.
Fabricating an active matrix LCD involves numerous steps, including substrate cleaning, substrate patterning, alignment layer formation, substrate joining and liquid crystal injection, and packaging. In substrate cleaning, alien substances are removed from the substrate. Substrate cleaning is usually performed both before and after substrate patterning of upper and lower substrates. Substrate patterning includes patterning an upper substrate and a lower substrate to incorporate required elements. The upper substrate is provided with elements such as color filters, a common electrode and a black matrix. The lower substrate is provided with elements such as data lines and gate lines, thin film transistors (TFT) arranged at intersections of the data lines and the gate lines, and a pixel electrodes. The pixel electrodes are formed at pixel areas between the data lines and the gate lines. Substrate joining and liquid crystal injection usually includes coating an alignment layer (orientation film) on a lower substrate, joining an upper substrate to the lower substrate, and injecting a liquid crystal into a gap that is formed between the lower and upper substrates. The injection hole for the liquid crystal is then sealed. In packaging, a tape carrier package (TCP) is mounted with gate drive integrated circuits (IC) and data drive integrated circuits in electrical contact with pads on the substrate.
A substrate joining and liquid crystal injection process will be described in more detail with reference to FIG. 1. FIG. 1 illustrates a conventional LCD fabrication process from a coating of an alignment layer until an inspecting step.
First, at step S2, a polyimide is coated on a substrate to provide an alignment layer. After being coated, the surface of the alignment layer is rubbed by a rubbing cloth or paper to produce a surface layer of polyimide molecules that are aligned in a constant direction, reference step S4. After rubbing, if the substrate being processed is an upper substrate, a stripe-shaped sealant is formed along the outer edge of the upper substrate, which is provided with color filters, reference step S6. During this process the sealant is not placed over a liquid crystal injection hole. However, if the substrate being processed is a lower substrate, spacers are sprayed onto the lower substrate, which includes an array of TFT""s, see step S8. This help prevent the upper substrate and the lower substrate from sticking fast to each other after a later joining (step S12). After step S8, silver (Ag) is coated onto the lower substrate to enable an electrical connection between the upper substrate and the lower substrate, reference step S10.
After steps S6 (upper substrate) or step S10 (lower substrate), the upper substrate is joined to the lower substrate using the stripe-shaped sealant formed along the edge of the upper substrate, reference step S12. After the upper substrate and the lower substrate are joined, the liquid crystal display panel is cut into smaller panels, reference step S14. Then, a liquid crystal is injected through a liquid crystal injection hole defined in the upper substrate of each of the cut panels, step S16. After the liquid crystal is injected, the liquid crystal injection holes is sealed with a sealant, reference step S18. Any liquid crystal that leaked during the liquid crystal injection step is then cleaned up, reference step 20. Finally, as step S22, the quality of the liquid crystal display panel is inspected.
In the conventional substrate joining/liquid crystal injection process described above, since the liquid crystal is injected through a liquid crystal injection hole after the joining of the upper substrate to the lower substrate, a considerable period of time is required to perform the injection. Furthermore, some of the liquid crystal leaks out of the liquid crystal injection hole after injection. Additionally, as the LCD gets larger, the injection of the liquid crystal becomes less uniform.
Accordingly, it is an object of the present invention to provide a method of fabricating a liquid crystal display that is capable of a reduced liquid crystal injection time and a more uniform injection.
To achieve these and other objects of the invention, a method of fabricating a liquid crystal display device according to an embodiment of the present invention includes forming a semi-solid sealant having a closed-loop shape on one of the substrates. A liquid crystal is then located in the sealant area. The substrates are then joined together, beneficially using a vacuum, with the sealant sealing the liquid crystal layer in place.
The method of fabricating a liquid crystal display device further includes the step of forming a spacer on at least one of the substrates.
The method of fabricating a liquid crystal display device further includes the step of exposing the sealant with ultraviolet light. Such exposure is beneficially performed at atmospheric pressure.
A method of fabricating a liquid crystal panel having a plurality of unit cells according to another embodiment of the present invention includes forming a sealant on at least a first substrate of unit cells, with the sealant being semi-solid and having a closed loop shape. Then, locating a liquid crystal layer in the closed loop region, and then joining a second substrate to the first substrate. The liquid crystal panel is then cut into a plurality of unit cells. The step of joining is beneficially performed in a vacuum. The process further includes forming a spacer on at least one of the substrates. Beneficially, the sealant is cured by light, preferably ultraviolet light. Curing is beneficially performed at atmospheric pressure.
Additional features and advantages of the invention will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.